Why does it start at 140? (LMIC_setSeqnoUp(140))

Paul_Stewart · May 23, 2019, 1:57am

Hi All,

I noticed when using a lot of LMIC examples, the frame counter starts at 140 when joined for the first time.

Is there a reason for this?

Can I set it to just start from 1?

Cheers
Paul

jreiss · May 23, 2019, 2:02pm

There is no reason to set FCNT to 140 after join.
0 or 1 would be normal.

Looks like it found its way into example code.

The Semtech LMIC client sets the FCNT to 0 in stateJustJoined()

github.com

lorabasics/basicmac/blob/master/lmic/lmic.c

// Copyright (C) 2016-2019 Semtech (International) AG. All rights reserved.
// Copyright (C) 2014-2016 IBM Corporation. All rights reserved.
//
// This file is subject to the terms and conditions defined in file 'LICENSE',
// which is part of this source code package.

//! \file
#include "lmic.h"

#if !defined(MINRX_SYMS)
#define MINRX_SYMS 5
#endif // !defined(MINRX_SYMS)
#define PAMBL_SYMS_BCN BCN_PREAMBLE_LEN
#define PAMBL_SYMS     STD_PREAMBLE_LEN
#define PAMBL_FSK  5
#define PRERX_FSK  2
#define RXLEN_FSK  (PRERX_FSK+5+3) // rx preamble and sync word
#define BCN_100PPM_ms 13   // 13ms = 128sec*100ppm which is roughly +/-100ppm

#define BCN_INTV_osticks       sec2osticks(BCN_INTV_sec)

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Paul_Stewart · May 23, 2019, 9:37pm

Ok thanks, just thought there may have been some kind of reason that I didn’t realize

system · July 22, 2019, 9:37pm

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